The authors at Shenzhen University greatly acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 51520105012 and 51278303) and the (Key) Project of Department of Education of Guangdong Province. (No.2014KZDXM051). They also thank the Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, College of Civil Engineering at Shenzhen University for providing testing facilities and equipment.

1. Testing the Specimen and the Manufacturing Process
<ol>
	<li>Acquire a 500 mm long, 14 mm diameter plain steel bar (grade Q235) for the manufacturing of the test specimens.</li>
	<li>Polish the surface of the bar using a fine sandpaper to remove the mill scales on the surface.</li>
	<li>Cut the bar at 30 mm and 470 mm from its left end, as shown in Figure 1, using a cutting machine.</li>
	<li>Measure the weights of the three bar specimens, using a digital electronic sca...

<ol>
	<li>Cavaco, E. S., Bastos, A., Santos, F. A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+corrosion+on+the+behaviour+of+precast+concrete+floor+systems.">Effects of corrosion on the behaviour of precast concrete floor systems.</a> Construction &amp; Building Materials. 145, (2017).</li><li>Cavaco, E. S., Neves, L. A. C., Casas, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+robustness+to+corrosion+in+the+life+cycle+assessment+of+an+existing+reinforced+concrete+bridge.">On the robustness to corrosion in the life cycle assessment of an existing reinforced concrete bridge.</a> Structure and Infrastructure Engineering. 14 (2), 137-150 (2017).</li><li>Muthulingam, S., Rao, B. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-uniform+corrosion+states+of+rebar+in+concrete+under+chloride+environment.">Non-uniform corrosion states of rebar in concrete under chloride environment.</a> Corrosion Science. 93, 267-282 (2015).</li><li>Apostolopoulos, C. A., Papadakis, V. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consequences+of+steel+corrosion+on+the+ductility+properties+of+reinforcement+bar.">Consequences of steel corrosion on the ductility properties of reinforcement bar.</a> Construction &amp; Building Materials. 22 (12), 2316-2324 (2008).</li><li>Fernandez, I., Bair&#225;n, J. M., Mar&#237;, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+effects+on+the+mechanical+properties+of+reinforcing+steel+bars.+Fatigue+and+&#963;+-+&#949;+behavior.">Corrosion effects on the mechanical properties of reinforcing steel bars. Fatigue and &#963; - &#949; behavior.</a> Construction &amp; Building Materials. 101, 772-783 (2015).</li><li>Papadopoulos, M. P., Apostolopoulos, C. A., Zervaki, A. D., Haidemenopoulos, G. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+of+exposed+rebars,+associated+mechanical+degradation+and+correlation+with+accelerated+corrosion+tests.">Corrosion of exposed rebars, associated mechanical degradation and correlation with accelerated corrosion tests.</a> Construction &amp; Building Materials. 25 (8), 3367-3374 (2011).</li><li>Castro, H., Rodriguez, C., Belzunce, F. J., Canteli, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+and+corrosion+behaviour+of+stainless+steel+reinforcing+bars.">Mechanical properties and corrosion behaviour of stainless steel reinforcing bars.</a> Journal of Materials Processing Technology. 143 (1), 134-137 (2003).</li><li>Almusallam, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+degree+of+corrosion+on+the+properties+of+reinforcing+steel+bars.">Effect of degree of corrosion on the properties of reinforcing steel bars.</a> Construction &amp; Building Materials. 15 (8), 361-368 (2001).</li><li>Papadopoulos, M. P., Apostolopoulos, C. A., Alexopoulos, N. D., Pantelakis, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+salt+spray+corrosion+exposure+on+the+mechanical+performance+of+different+technical+class+reinforcing+steel+bars.">Effect of salt spray corrosion exposure on the mechanical performance of different technical class reinforcing steel bars.</a> Materials &amp; Design. 28 (8), 2318-2328 (2007).</li><li>Zhang, W., Song, X., Gu, X., Li, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensile+and+fatigue+behavior+of+corroded+rebars.">Tensile and fatigue behavior of corroded rebars.</a> Construction &amp; Building Materials. 34 (5), 409-417 (2012).</li><li>Clark, L. A., Chan, A. H. C., Du, Y. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Residual+capacity+of+corroded+reinforcing+bars.">Residual capacity of corroded reinforcing bars.</a> Magazine of Concrete Research. 57 (3), 135-147 (2005).</li><li>Chan, A. H. C., Clark, L. A., Du, Y. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+corrosion+on+ductility+of+reinforcing+bars.">Effect of corrosion on ductility of reinforcing bars.</a> Magazine of Concrete Research. 57 (7), 407-419 (2005).</li><li>Zhu, W., Fran&#231;ois, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+of+the+reinforcement+and+its+influence+on+the+residual+structural+performance+of+a+26-year-old+corroded+RC+beam.">Corrosion of the reinforcement and its influence on the residual structural performance of a 26-year-old corroded RC beam.</a> Construction &amp; Building Materials. 51 (2), 461-472 (2014).</li><li>Fran&#231;ois, R., Khan, I., Dang, V. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+corrosion+on+mechanical+properties+of+steel+embedded+in+27-year-old+corroded+reinforced+concrete+beams.">Impact of corrosion on mechanical properties of steel embedded in 27-year-old corroded reinforced concrete beams.</a> Materials &amp; Structures. 46 (6), 899-910 (2013).</li><li>Torres-Acosta, A. A., Castro-Borges, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion-Induced+Cracking+of+Concrete+Elements+Exposed+to+a+Natural+Marine+Environment+for+Five+Years.">Corrosion-Induced Cracking of Concrete Elements Exposed to a Natural Marine Environment for Five Years.</a> Corrosion. 69 (11), 1122-1131 (2013).</li><li>Li, D., Wei, R., Du, Y., Guan, X., Zhou, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+methods+of+geometrical+parameters+and+amount+of+corrosion+of+steel+bar.">Measurement methods of geometrical parameters and amount of corrosion of steel bar.</a> Construction &amp; Building Materials. 154, 921-927 (2017).</li><li>Kashani, M. M., Crewe, A. J., Alexander, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+a+3D+optical+measurement+technique+for+stochastic+corrosion+pattern+analysis+of+reinforcing+bars+subjected+to+accelerated+corrosion.">Use of a 3D optical measurement technique for stochastic corrosion pattern analysis of reinforcing bars subjected to accelerated corrosion.</a> Corrosion Science. 73 (13), 208-221 (2013).</li><li>Tang, F., Lin, Z., Chen, G., Yi, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+corrosion+pit+measurement+and+statistical+mechanical+degradation+analysis+of+deformed+steel+bars+subjected+to+accelerated+corrosion.">Three-dimensional corrosion pit measurement and statistical mechanical degradation analysis of deformed steel bars subjected to accelerated corrosion.</a> Construction &amp; Building Materials. 70 (2), 104-117 (2014).</li><li>Zhang, W., Zhou, B., Gu, X., Dai, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probability+Distribution+Model+for+Cross-Sectional+Area+of+Corroded+Reinforcing+Steel+Bars.">Probability Distribution Model for Cross-Sectional Area of Corroded Reinforcing Steel Bars.</a> Journal of Materials in Civil Engineering. 26 (5), 822-832 (2013).</li><li>Wang, X. G., Zhang, W. P., Gu, X. L., Dai, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+residual+cross-sectional+areas+of+corroded+bars+in+reinforced+concrete+structures+using+easy-to-measure+variables.">Determination of residual cross-sectional areas of corroded bars in reinforced concrete structures using easy-to-measure variables.</a> Construction &amp; Building Materials. 38, 846-853 (2013).</li><li>Stewart, M. G., Al-Harthy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pitting+corrosion+and+structural+reliability+of+corroding+RC+structures:+Experimental+data+and+probabilistic+analysis.">Pitting corrosion and structural reliability of corroding RC structures: Experimental data and probabilistic analysis.</a> Reliability Engineering &amp; System Safety. 93 (3), 373-382 (2008).</li><li>Darmawan, M. S., Stewart, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Spatially+Variable+Pitting+Corrosion+on+Structural+Reliability+of+Prestressed+Concrete+Bridge+Girders.">Effect of Spatially Variable Pitting Corrosion on Structural Reliability of Prestressed Concrete Bridge Girders.</a> Australian Journal of Structural Engineering. 6 (2), 147-158 (2015).</li><li>Stewart, M. G., Mullard, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+time-dependent+reliability+analysis+of+corrosion+damage+and+the+timing+of+first+repair+for+RC+structures.">Spatial time-dependent reliability analysis of corrosion damage and the timing of first repair for RC structures.</a> Engineering Structures. 29 (7), 1457-1464 (2007).</li><li>Kashani, M. M., Lowes, L. N., Crewe, A. J., Alexander, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Finite+element+investigation+of+the+influence+of+corrosion+pattern+on+inelastic+buckling+and+cyclic+response+of+corroded+reinforcing+bars.">Finite element investigation of the influence of corrosion pattern on inelastic buckling and cyclic response of corroded reinforcing bars.</a> Engineering Structures. 75, 113-125 (2014).</li><li>Apostolopoulos, C. A., Demis, S., Papadakis, V. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chloride-induced+corrosion+of+steel+reinforcement+-+Mechanical+performance+and+pit+depth+analysis.">Chloride-induced corrosion of steel reinforcement - Mechanical performance and pit depth analysis.</a> Construction and Building Materials. 38, 139-146 (2013).</li><li>Imperatore, S., Rinaldi, Z., Drago, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Degradation+relationships+for+the+mechanical+properties+of+corroded+steel+rebars.">Degradation relationships for the mechanical properties of corroded steel rebars.</a> Construction and Building Materials. , 219-230 (2017).</li><li>Kashani, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+effect+on+inelastic+buckling+behaviour+of+accelerated+pitted+1+corroded+bars+in+porous+media.">Size effect on inelastic buckling behaviour of accelerated pitted 1 corroded bars in porous media.</a> Journal of Materials in Civil Engineering. 29 (7), (2017).</li><li>Meda, A., Mostosi, S., Rinaldi, Z., Riva, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+evaluation+of+the+corrosion+influence+on+the+cyclic+behaviour+of+RC+columns.">Experimental evaluation of the corrosion influence on the cyclic behaviour of RC columns.</a> Engineering Structures. 76, 112-123 (2014).</li><li>Kashani, M. M., Crewe, A. J., Alexander, N. 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Figure 6A and 6B show that the measured diameters of the non-corroded bar specimen do not vary significantly along its length. The maximum difference between the measured diameters along the bar length is only about 0.11 mm with a maximum deviation of 0.7%. This indicates that the geometry of a non-corroded bar can be well evaluated using a Vernier caliper. However, the measured diameters at different angles of the same cross-section differ consistently and considerably from...

Corrosion of a steel bar is one of the principal reasons for deterioration of a concrete structure and is caused by concrete carbonation and/or chloride intrusion. In concrete carbonation, corrosion tends to be generalized; while in chloride intrusion, it becomes more localized1,2. No matter what the causes are, corrosion cracks the concrete cover from radial expansion of corrosion products, deteriorates the bond between a steel bar and its surrounding concrete, penetrates the bar surfaces, and decreases the bar cross-sectional area considerably3,4.
Due to the non-homogeneity of structural concrete and variations in the service environment, corrosion of a steel bar occurs randomly over its surface and along its length with great uncertainty. Contrary to the generalized uniform corrosion caused by concrete carbonation, the pitting corrosion caused by chloride intrusion causes attack penetration. Furthermore, it causes the residual section of a corroded bar to vary considerably among the bar surface and length. As a result, the bar strength and bar ductility decrease. Extensive research has been performed to study the effects of corrosion on mechanical properties of a steel bar5,6,7,8,9,10,11,12,13,14,15. However, less attention has been given to the measurement methods of morphological parameters and corrosion characteristics of steel bars.
Some researchers have used mass loss to evaluate the amount of corrosion of a steel bar5,10,11,14. However, this method can only be used to determine the average value of the residual sections and cannot measure the distribution of the sections along its length. Zhu and Franco have improved this method by cutting a single steel bar into a series of short segments and weighing each segment to determine variations of the areas of the residual sections along its length13,14. However, this method causes extra loss of the steel material during the cutting and cannot touch the minimum residual section of the corroded bar exactly, which dominates its bearing capacity. A Vernier caliper is also used to measure the geometric parameters of a steel bar14,15. However, the residual section of a corroded bar is very irregular, and there is always a significant deviation between the measured and actual sectional dimensions of a corroded bar. Based on Archimedes&#39; principle, Clark et al. adopted the drainage method to measure the residual sections of a corroded bar along its length, but displacement of the bar was manually controlled without significant accuracy in this case11. Li et al. improved this drainage method by using an electric motor to automatically control the displacement of a steel bar and measure results more accurately16. Finally, over the past few years, with the development of 3D scanning technology, this method has been used to measure the geometric dimensions of a steel bar17,18,19,20. Using 3D scanning, the diameter, residual area, centroid, eccentricity, moment of inertia, and corrosion penetration of a steel bar can be precisely acquired. Although researchers have used these methods in different experimental settings, there has not been a comparison and evaluation of the methods with respect to their precision, suitability and applicability.
Corrosion, particularly pitting corrosion, compared to generalized corrosion, not only changes the mechanical properties of corroded bars but also decreases the residual bearing capacity and service life of concrete structures. More accurate measurements of morphological parameters of corroded steel bars for the spatial variability of corrosion along bar length are imperative for more reasonable assessments of bar mechanical properties. This will help evaluate the safety and reliability of reinforced concrete (RC) structures damaged by corrosion more precisely21,22,23,24,25,26,27,28,29.
This protocol compares the five discussed methods for measuring the geometry and amount of corrosion of a steel bar. A single, 500 mm long and 14 mm in diameter, plain round bar was used as the specimen and subjected to accelerated corrosion in the lab. Its morphology and level of corrosion were carefully measured before and after using each method, including mass loss, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro computed tomography (XCT). Finally, the applicability and suitability of each were evaluated.
It should be noted that the ribbed bars embedded in concrete, not the plain bars exposed to air, are commonly used in concrete structures and subjected to corrosion. For ribbed bars, the Vernier caliper may not be as easily applied. Because these bars corrode in concrete, their surface penetration is more irregular compared to bars exposed to air11. However, this protocol is geared towards the applicability of analysis of different measurement methods on the same bar; therefore, it uses a naked plain bar as the specimen to eliminate the influence of ribs and concrete non-homogeneity on morphological parameter measurements. Further work on the measurement of corroded ribbed bars using other methods may be carried out in the future.

<table>
	<tbody>
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			<td>Plastic ruler</td>
			<td>Deli Group Co.,Ltd.</td>
			<td>No.6240</td>
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			<td>white paint pen</td>
			<td>SINO PATH Enterprises.,Ltd.</td>
			<td>SP-110</td>
			<td></td>
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			<td>Tube with Branch</td>
			<td>Customized-made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Measurement cylinder</td>
			<td>Beijing Huake Bomex Glass Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>500mL Beaker</td>
			<td>Beijing Huake Bomex Glass Co. , Ltd.</td>
			<td>CP-201</td>
			<td></td>
		</tr>
		<tr>
			<td>sandpaper</td>
			<td>Shanghai Noon Decoration Material Co., Ltd.</td>
			<td>P04</td>
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		<tr>
			<td>white developer</td>
			<td>SHANGHAI XINMEIDA FLAW DETECTION MATERIAL CO., LTD.</td>
			<td>FA-5</td>
			<td></td>
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			<td>Reagents</td>
			<td></td>
			<td></td>
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			<td>epoxy resin adhesive</td>
			<td>Hunan Baxiongdi New Material Co., Ltd.</td>
			<td>DY&#183;E&#183;44</td>
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			<td>epoxy hardener</td>
			<td>Hunan Baxiongdi New Material Co., Ltd.</td>
			<td>DY&#183;EP</td>
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			<td>Dongguan Dongjiang Chemical Reagent Co., Ltd.</td>
			<td>AR-2500ml</td>
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			<td>Xilong Chemical Co., Ltd.</td>
			<td>AR-500g</td>
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			<td>Equipment</td>
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			<td>Digital electronic scale</td>
			<td>Kaifeng Group Co., Ltd.</td>
			<td>Model JCS-0040</td>
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			<td>Digital vernier caliper</td>
			<td>Shanghai Measuring &#38; Cutting Tool Works Co., Ltd.</td>
			<td>Model ST-089-229-090</td>
			<td></td>
		</tr>
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			<td>Cutting machine</td>
			<td>Robert Bosch GmbH</td>
			<td>TCO2000</td>
			<td></td>
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			<td>3D reconstructed X-ray microscope</td>
			<td>XRADIA</td>
			<td>Model MICROXCT-400</td>
			<td></td>
		</tr>
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			<td>3D scanner</td>
			<td>HOLON Three-dimensional Technology(Shenzhen) Co.,Ltd.</td>
			<td>Model HL-3DX+</td>
			<td></td>
		</tr>
		<tr>
			<td>Electromechanical Universal Testing Machine</td>
			<td>MTS SYSTEMS (China) Co., Ltd.</td>
			<td>Model C64.305</td>
			<td></td>
		</tr>
	</tbody>
</table>

applicability analysis of assessment methods for morphological parameters of corroded steel bars

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

Figure 6 shows the diameters of the 500 mm long non-corroded bar specimen at angles of 0&#176;, 45&#176;, 90&#176;, and 135&#176; for each section along its length measured using Vernier calipers. The bars were then cut into three parts, as shown in Figure 1.
Figure 7 presents the cross-sectional areas of the non-corroded bar specimens alon...

Watch this Scientific Journal Video about Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars at JoVE.com

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars

This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly ...

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6.3K 조회수.  Shenzhen University. This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).